Envelopes having perforated sections to facilitate the opening thereof have been long known, although most of the prior structures contemplated have not achieved much success. Perhaps those which have achieved the greatest success are those which embody tear strips of various kinds, and these are especially used in larger envelopes and small sealed mailing boxes. The recent advent of computer generated mail has also led to the increased use of certain types of form envelopes having tearable portions for facilitating opening, or tear strips with pull tabs.
There are many reasons why the prior constructions have not achieved great success, particularly in common envelopes as compared with envelopes used for the mailing of computer generated material. Among these reasons are aesthetic insufficiencies in the prior constructions; constructions which are too complex and thus too expensive to manufacture and sell at a reasonable price; the use of inadequate tear lines which comprise a single line or series of co-linear cuts, scores or perforations, leading to poor tearability; and the use of exposed tear lines which are subject to accidental tearing.
Among the problems which the prior envelopes have is that they are often difficult to open in spite of being provided with tear lines. Sometimes these envelopes are possible to open, but not quickly. Some of the prior envelopes cannot be opened safely without damaging the contents. In some cases, even though the envelope may be easy to open, it is nevertheless difficult to remove the contents.
Among the patent literature, prior constructions having exposed tear lines are shown by Pedrick U.S. Pat. No. 3,046,662; Robbins U.S. Pat. No. 3,620,441; Grotefend U.S. Pat. No. 3,652,008; Nixon et al U.S. Pat. No. 4,166,538 and Meeker et al U.S. Pat. No. 4,470,511. Patents which show tear strips in which the tear lines are exposed include Stillwell U.S. Pat. No. 890,538; Snider U.S. Pat. No. 1,044,935; Caldwell U.S. Pat. No. 3,392,905 and Christiansen et al U.S. Pat. No. 3,650,463. The Kleinfelot U.S. Pat. No. 669,203 shows both these possibilities. All these patents show constructions with the defects mentioned above which are inherent in having the tear line or lines exposed.
Several U.S. patents show constructions in which the tear line lies adjacent the edge of the flap, and these include Godley U.S. Pat. No. 1,306,224; Hinchman U.S. Pat. No. 717,993 and Brobst U.S. Pat No. D-26,378. These patents go back more than sixty-five years, and have never achieved success. Moreover, the tear lines of these patents are not really hidden, but lie along the edge of the flap where they may be easily seen.
Lastly, the patent to Bielawski U.S. Pat. No. 4,093,074 discloses two embodiments of envelopes which, while significantly improved compared to other prior constructions, still do not solve the problems outlined above. In the embodiment of FIGS. 1-3, a special and relatively complex blank must be used resulting in an unduly expensive envelope, and also the envelope lacks security because of the limited gluing area, which incidentally must be carefully aligned with relatively small dog-ear flaps. The embodiment of FIGS. 4-6 requires instructions as to how the envelope is to be opened, as it is unnatural to attempt to open the lower part of the body of the envelope. In addition, because of the location of the tear lines in this embodiment, the construction is limited to only certain kinds of envelopes, and such a construction is not available to a wide variety of envelope constructions.